Optical recording disks of the write-once, rewritable and other types have been of great interest as high capacity information bearing media. Optical recording disks of one type use a dye film as a recording layer. From a structural aspect, there are known disks of the air-sandwich structure having an air space on a recording layer or dye film and disks of the close contact type having a reflective layer in close contact with a recording layer composed of a dye film which can be reproduced in accordance with the compact disk (CD) standards. See Nikkei Electronics, Jan. 23, 1989, No. 465, page 107; the Functional Dye Department of the Kinki Chemical Society, Mar. 3, 1989, Osaka Science & Technology Center; and Proceedings SPIE--The International Society for Optical Engineering, Vol. 1078, pp. 80-87, "Optical Data Storage Topical Meeting", 17-19, Jan. 1989, Los Angels.
For the dyes used to form the recording layers, indolenine series cyanine dyes are preferred because of heat resistance and water resistance as disclosed in Japanese Patent Application Kokai (JP-A) No. 24692/1984 and other patent publications. However, the indolenine series cyanine dyes have the drawback that they tend to deteriorate with reproduction, that is, by repetitive irradiation of reproducing light or optically deteriorate during light room storage. It was thus proposed and has been practiced to use the dye in admixture with a metal complex quencher as disclosed in JP-A 59795/1984. Among such metal complexes, bis(phenylenedithiol) nickel complexes are highly effective in protecting the cyanine dyes from deterioration by repetitive reproduction and optical deterioration. Undesirably, these complexes are low soluble as demonstrated by a solubility of less than 1% in alcohols such as methanol. It is then impossible to form a recording layer by coating a solution of the complex in such a solvent. Also the metal complex has an absorption wavelength of 700 to 1,000 nm and can affect the absorption of the dye, eventually resulting in a lowering of reflectivity and hence a lowering of reproduced output.
With regard to the dyes, reference is made to "Chemistry of Functional Dyes", CMC Publishing K.K., pages 74-76 as well as the following patent applications.
______________________________________ Japanese Patent Application Kokai (JP-A) Nos. ______________________________________ 24692/1984 55794/1984 55795/1984 81194/1984 83695/1984 18387/1985 19586/1985 19587/1985 35054/1985 36190/1985 36191/1985 44554/1985 44555/1985 44389/1985 44390/1985 47069/1985 20991/1985 71294/1985 54892/1985 71295/1985 71296/1985 73891/1985 73892/1985 73893/1985 83892/1985 85449/1985 92893/1985 159087/1985 162691/1985 203488/1985 201988/1985 234886/1985 234892/1985 16894/1986 11292/1986 11294/1986 16891/1986 08384/1986 14988/1986 163243/1986 210539/1986 30083/1987 32132/1987 31792/1987 Japanese Patent Application No. 54013/1985 ______________________________________